Drug & supplement interaction

Branched-chain Amino Acids (bcaa) + Carbidopa, Levodopa

Carbidopa, Levodopa brand names: Sinemet CR, Sinemet, Rytary, Dhivy.

Major Interaction
Medically reviewed by · Updated September 2026
The bottom line Major

Branched-chain Amino Acids (bcaa) has a major interaction with Carbidopa, Levodopa. BCAAs in large doses can reduce the effects of levodopa.

Read the full interaction report
SeverityMajor
LikelihoodProbable
EvidenceB
What do Severity, Likelihood & Evidence mean?
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Interaction report

Branched-chain Amino Acids (bcaa) and Carbidopa, Levodopa

Here is the interaction we found between these two, with the evidence behind it.

Major

LEVODOPA

Why this applies to Carbidopa, Levodopa

Carbidopa, Levodopa falls under LEVODOPA — the group Branched-chain Amino Acids (bcaa) interacts with.

BCAAs in large doses can reduce the effects of levodopa.
BCAAs may compete with levodopa for transport systems in the intestine and brain and decrease the effectiveness of levodopa. Small clinical studies how that concomitant ingestion of protein or high doses of leucine or isoleucine (100 mg/kg) and levodopa can exacerbate tremor, rigidity, and the "on-off" syndrome in patients with Parkinson disease.
Severity Major Likelihood Probable Evidence B

Interaction has not been documented in well-controlled studies, however, the interaction has been demonstrated in some small human studies or in controlled animal studies in conjunction with multiple case reports..

Dr. Brian Staiger, PharmD, BCPS
Dr. Brian Staiger explains PharmD, Clinical Pharmacist

Here's something worth knowing if you take Sinemet, Rytary, or Dhivy for Parkinson's. Levodopa is an amino acid itself, and it hitches a ride on the same transport system in your gut and at the brain that branched-chain amino acids use. When you load up on BCAAs, they can crowd out levodopa and keep less of it from reaching the brain where it turns into dopamine.

The practical worry: your medicine may work less well, so you could notice more tremor, stiffness, slowness, or rougher "on-off" swings. Small studies back this up, mostly at high doses (think concentrated supplements, not a normal meal). Don't change anything on your own, but do mention your BCAA use to your pharmacist or doctor so timing can be sorted out.

Contact Dr. Brian directly if you have additional questions on this interaction
References
  1. Rosen HM, Yoshimura N, Hodgman JM, Fischer JE. Plasma amino acid patterns in hepatic encephalopathy of differing etiology. Gastroenterology 1977;72:483-7. DOI
  2. DiPiro JT, Talbert RL, Yee GC, et al; eds. Pharmacotherapy: A pathophysiologic approach. 4th ed. Stamford, CT: Appleton & Lange, 1999.
  3. Nutt JG, Woodward WR, Hammerstad JP, et al. The "on-off" phenomenon in Parkinson's disease. Relation to levodopa absorption and transport. N Engl J Med 1984;310:483-8. PubMed
  4. Baruzzi A, Contin M, Riva R, et al. Influence of meal ingestion time on pharmacokinetics of orally administered levodopa in parkinsonian patients. Clin Neuropharmacol 1987;10:527-37. PubMed
  5. Juncos JL, Fabbrini G, Mouradian MM, et al. Dietary influences on the antiparkinsonian response to levodopa. Arch Neurol 1987;44:1003-5. PubMed
  6. Eriksson T, Granerus AK, Linde A, et al. "On-off" phenomenon in Parkinson's disease: relationship between dopa and other large neutral amino acids in plasma. Neurology 1988;38:1245-8. PubMed

What These Ratings Mean

Every interaction above is graded three ways — here’s the key to each label.

Severity how clinically significant the interaction is
Major

Clinically significant. Avoid the combination, or use only under close professional supervision.

Moderate

Usually worth avoiding or managing — may need monitoring, a dose change, or timing apart.

Minor

Generally not serious. Be aware of it and mention it to your pharmacist.

Likelihood how strong the evidence is that the interaction actually happens in people
  • LikelyWell-controlled human studies have demonstrated the likely existence of this interaction.
  • ProbableInteraction has not been documented in well-controlled studies, however, the interaction has been demonstrated in some small human studies or in controlled animal studies in conjunction with multiple case reports.
  • PossibleInteraction has been documented in animal or in lab research, or the interaction has been documented in humans but is limited to case reports or conflicting clinical research exists.
  • UnlikelyInteraction has been demonstrated in animal or in lab research but has been shown not to occur in humans.
Evidence the quality of the studies behind the rating (graded A–D)
  • AHigh-quality meta-analysis (quantitative systematic review).
  • BCase-control study.
  • CConsensus.
  • DAnecdotal evidence.

These ratings are for information only. Never start, stop, or otherwise change your therapy before speaking with your provider.

Keep it in perspective

Branched-chain Amino Acids (bcaa) Also Interacts With Other Medications

Branched-chain Amino Acids (bcaa) has 4 major, 86 moderate known drug interactions in our database — the Carbidopa, Levodopa one above is one of them. If you take anything else, check it against the full list below.

Major 4 Moderate 86 No known interaction 2,740 (incl. Carbidopa, Levodopa)
Taking anything else?

Check Another of Your Medications Against Branched-chain Amino Acids (bcaa)

Covers the 2,830 medications we’ve checked against Branched-chain Amino Acids (bcaa). Pick one to open its full report.

Everything else you take

See Every Supplement That Interacts With Carbidopa, Levodopa

This page covers Branched-chain Amino Acids (bcaa) only. If you take other supplements — a multivitamin, a sleep aid, something for joints — the Carbidopa, Levodopa page lists 43 supplements it has a documented interaction with, worst first, each one explained.

The most serious there right now: Activated Charcoal (major), Cowhage (major), Indian Snakeroot (major), Magnesium (major) and Phenylalanine (major).

By severity: 8 major · 24 moderate · 11 minor.

From our pharmacist’s overview on the Carbidopa, Levodopa page

“Carbidopa/levodopa (Sinemet, Rytary) anchors Parkinson's treatment, and because symptom control hinges on how much levodopa actually reaches the brain, the 43 supplements and herbs on this list deserve real respect before you add any of them. Eight carry a major rating, and almost all of the serious entries weaken the drug rather than…”

Reviewed by 2 · Jul 18, 2026

Open the Carbidopa, Levodopa interaction page

How much people look this up

Where Branched-chain Amino Acids (bcaa) and Carbidopa, Levodopa Sit Against Everything Else

Out of every supplement and medication people look up on HelloPharmacist, here is where these two land this week — and which way each has been moving.

Supplement Branched-chain Amino Acids (bcaa)
Steady interest

#751 of 1,452 supplements looked up here in the last 7 days

29 days ago today
Medication Carbidopa, Levodopa
Top 25%

#295 of 2,830 medications looked up here in the last 7 days

29 days ago today

Position among everything looked up on this site, not a measure of how commonly either one is used or how important it is. A supplement can climb this list because of a news story. It counts every request to the page, automated ones included, and nothing here identifies anyone.

Supplement

About Branched-chain Amino Acids (bcaa)

What is Branched-chain Amino Acids (bcaa)?

  • Muscle building and exercise recovery
  • Reducing exercise fatigue
  • Preserving muscle during weight loss
  • Liver disease support
  • Tardive dyskinesia (under study)

Branched-chain amino acids (leucine, isoleucine, and valine) are essential nutrients commonly taken by athletes for muscle support and recovery. Evidence shows modest benefits for some uses, but a balanced protein source usually provides the same amino acids. They are generally well tolerated for most healthy adults, but check with your pharmacist or doctor before use, especially if you have a medical condition.

Read the full Branched-chain Amino Acids (bcaa) monograph & all interactions
Medication

About Levodopa and Carbidopa

What Is Levodopa and Carbidopa Used For?

Brand names: Sinemet CR, Sinemet, Rytary, Dhivy

Levodopa and carbidopa treats Parkinson’s disease, post-encephalitic parkinsonism (parkinsonism after brain inflammation), and parkinsonism that may follow carbon monoxide or manganese intoxication. This applies to the oral tablets, orally disintegrating tablets, and extended-release tablets and capsules.

Duopa (enteral suspension) is used specifically for motor fluctuations in people with advanced Parkinson’s disease. Crexont is labeled for adults.

See full Levodopa and Carbidopa drug information
Keep checking

Other Drugs & Branched-chain Amino Acids (bcaa)

Browse every other medication we’ve checked against Branched-chain Amino Acids (bcaa) — both the ones with a known interaction and the ones without. Select any drug for the full detail.

4Major
86Moderate
0Minor
2,739No known interaction
4 Major 86 Moderate 2,739 No interaction
Major

4 interactions

Moderate

86 interactions

Showing 60 of 86 moderate interactions — see all 86 on the Branched-chain Amino Acids (bcaa) page.

No interaction 2,739 drugs checked — show the list

We also checked Branched-chain Amino Acids (bcaa) against these medications and found no known interaction in our sources. Open any page to confirm.

Showing the 60 most looked-up of 2,739 medications checked with no known interaction — see the full Branched-chain Amino Acids (bcaa) list.

See the full Branched-chain Amino Acids (bcaa) interactions page
See every supplement checked against Carbidopa, Levodopa, ranked by severity
Sources

Sources & How We Checked

Interaction details are evidence-graded and sourced from the Natural Medicines database. The medication overview comes from MedlinePlus.

Content is written and reviewed by licensed HelloPharmacist pharmacists. See our data sources and editorial standards for how this information is built and checked.

Parts of this content are provided by the Therapeutic Research Center, LLC.

DISCLAIMER: Currently this does not check for drug-drug interactions. This is not an all-inclusive comprehensive list of potential interactions and is for informational purposes only. Not all interactions are known or well-reported in the scientific literature, and new interactions are continually being reported. Input is needed from a qualified healthcare provider including a pharmacist before starting any therapy. Application of clinical judgment is necessary.

© 2021 Therapeutic Research Center, LLC

Keep exploring
Branched-chain Amino Acids (bcaa) monograph › Uses, safety, and every drug interaction in one place Carbidopa, Levodopa supplement interactions › Every supplement checked against Carbidopa, Levodopa, ranked by severity Levodopa and Carbidopa drug information › The full plain-English guide to this medication Supplement interaction checker › Check any supplement or product against your medications Browse medications A–Z › Every drug we've checked against herbs & supplements Ask a pharmacist › Free, personal answer from our licensed team
Pharmacist Counseling Corner

Taking Branched-chain Amino Acids (bcaa) and Carbidopa, Levodopa Together: Common Questions

Can you take Branched-chain Amino Acids (bcaa) with Carbidopa, Levodopa?
This is rated a major interaction, so the combination is best avoided unless your doctor or pharmacist has specifically told you otherwise. Read the full details on this page and confirm with your pharmacist before combining them.
How serious is the Branched-chain Amino Acids (bcaa) and Carbidopa, Levodopa interaction?
We rate it Major. This is a clinically significant combination that is generally best avoided, or used only under the direct supervision of your physician or pharmacist.

Written and reviewed by the HelloPharmacist editorial staff. Our editorial policy

Still Have a Question About Carbidopa, Levodopa and Branched-chain Amino Acids (bcaa)?

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This information is for education only and is not a substitute for professional medical advice. Always check with your pharmacist or doctor before starting, stopping, or combining supplements and medications.